Fluid material container with inclined slotted bottom having inductive stirring device adjacent thereto for an electric furnace



2,711,436 OTTOM June 1955 M. F. JONES ETAL FLUID MATERIAL CONTAINER WITHINCLINED SLOTTED B HAVING INDUCTIVE STIRRING DEVICE ADJACENT THERETO FORAN ELECTRIC FURNACE Filed Aug. 14, 1952 F l G. 1

5 m0 J wig w? NC a a Ma Y B atent @thce 2,711,436 ed June 21, 1%55 FLUIDMATERIAL CGNTAKNER WITH INCLIVED SLOTTED BOTTOM HAVING INDUCTIVE STIR-RING DEVICE ADJACENT THERETO FOR AN ELECTRIC FURNACE Maurice F. Jones,Pittsburgh, and Isaac Harter, In, and Temple W. Ratclifie, Beaver, Pa.,assignors, by direct and mesne assignments, to The Bahcock & WilcoxCompany, New York, N. Y., a corporation of New Jersey Application August14, 1952, Serial No. 394,252

11 Claims. (Cl. 13--2o) This invention relates to inductive stirring offluid materials in a container and, more particularly, to an improvedcontainer construction and a novel combinati .1 of inductive stirringmeans therewith.

Stirring of fluid materials in containers is frequently practiced forvarious reasons, such as to obtain uniform temperatures and uniformcomposition, to speed up reaction rates, and to control the direction ofmovement of the fluid material. When heat is transmitted to the body offluid material through its surface, a stirring action is desirable inorder to obtain uniform heat throughout the body particularly when it isdesire to avoid any substantial thermal gradient from top to bottom ofthe body.

It has been proposed to effect the stirring of the body of fluidmaterial inductively instead of by the present marual or mechanicalmethods, and various arrangements have been suggested to provide suchinductive stirring. These arrangements include those in which anelectric flux is applied to the body at a predetermined zone in order tocirculate the fluid material through this zone, the zone generallycomprising a restricted passage or the like in communication with themain body of fluid material. Coils are used to provide the flux, beingmounted in predetermined patterns on the container and suitablyenergized either with single or polyphase A. C.

While such inductive stirring is applicable to any electricallyconductive fluid material in a container, it has found particularapplication in the metal founding and handling art. In this art, it hasbeen applied principally to the stirring of the bath in meltingfurnaces, the term bath designating a body of hot metal with or withouta protective slag coating. The inductive stirring is designed to assureequalization of temperatures in the bath, acceleration of reactions, anduniformity of mixing of the elements, ingredients or constituents of thebath. One advantage is that the stirring promotes uniform temperaturesthroughout the bath even when the latter is spot heated, by one or moreelectric arcs playing on its surface.

This stirring is particularly important in the case of continuous metalcasting operations wherein, while molten metal is being poured into themold from one ladle, one or more additional ladies of molten metal arekept in stand-by relation in order to utilize effectively availablemelting furnace capacity in which the tapping times of the meltingfurnaces may not be readily coordinated with the initiation ofsuccessive ladle pours into the continuous casting mold. in order toassure equalization of temperature in the molten metal and substantialuniformity of composition therethrough, it is particularly desirable tostir the metal both during the time a ladle is being held in stand-byrelation and during the time molten metal is being poured therefrom.

It has been found that, when inductive stirring coils are applied to theusual type of ladle involving a metal shell having its inner surfacelined with refractory, an excessive amount of power is required toeffect the desired degree of stirring. This is due to the relativelylarge .ction in the effective field applied to the molten e "l as resultof eddy current losses in the metal shell. However, attempts to correctthis condition have not been satisfactory largely due to the fact that asuitable relatively rigid metal structure must be provided as a St ortfor the refractory lining.

While the container and associated inductive stirring mech nism of thepresent invention is applicable to the stirring of any electricallyconductive fluid material held in a container, the invention arrangementfinds particular applicability in the stirring of molten metal held in a"sortie", holding or pouring ladle. The invention will, titer-store, bedescribed, solely by way of giving a par cular example of theapplication of the invention ples, applied to the stirring of moltenmetal in refractory lined ladle.

nce with the present invention, the desired effect on the molten metalis produced with a ial reduction in power requirements over ed by priorart arrangements by interrupting the co tinuity of ma netic paths in theladle lining shell and isolating magnetic components from each other,this being effected While still providing adequate support for the ladlelining. In addition, adequate cooling for the induction coils isprovided. Both the electrical paths and the magnetic paths in thesupport structure are broken up into isolated sections. As a result,eddy current and 7 l in the ladle shell (re nearly eliminated, resul. uin lower power input to the induction coils being required to create thedesir d stirring effect.

To this end, the shell structure within the desirably n strength portionof the field of the induction devices is made of nonmagnetic materialand is formed of separate elements electrically and magneticallyinsulated from each other. Typically, at least the lower portion of theside wall of the ladle shell is formed of a nonm lilC metal, such ascertain of the stainless steels. The bottom wall of the shell is formedor" spaced, substaniially parallel, metal slats supported at their ends,in electrically insulated relation, on the lower margin of the shellside Wall.

It has been found further that, when the inductive stirring coils aremounted immediately adjacent the ladle, which is the most effectiveposition for insuring the maximum stirring effect on the molten metal,the coils become overheated. This is due to the combined elfect of thenormal temperature rise due to current flow through the coils augmentedby the relatively high ambient temperature in the immediate vicinity ofthe ladle. Further more, effective stirring with the usual flat bottomedladle of the prior art requires rather complicated coil arrangements ofrelatively large size and also requires complicated and expensive lowcycle A. C. generators of high amperage. This large amperage inputrequired, in prior art devices, to produce the necessary field strengthresults in such heating of the coils as to require water cooling of thelatter. This is undesirable, as it amounts to providing water under amolten steel bath with the attendant risk.

The particular inductive stirring arrangement of the invention permitsthe use of a relatively deep ladle which is advantageous from thestandpoint of having, for equal molten metal capacity, less surfaceexposed for heat dissipation or oxidation, and requiring a lesser amountof slag for cover purposes thereby reducing the potentialities ofchanging the composition of the metal by re action with the slag whilethe metal is in storage. The effectiveness of the stirring action isfurther enhanced by providing a sloping bottom wall for the ladle withthe inductive stirring arrangement disposed adjacent this Wall and soarranged that the field effect on the molten the and through the slatsextending upwardly along the I under surface of the sloping bottom wall.The slats may comprise bars or may comprise rectangular or cylindricaltubes arranged in spaced relation. The cooling effect may be augmentedby forcing air through or between the slats.

The inductive stirring arrangement preferably comprises a plurality ofcoils or coil sections arranged in a toothed or slotted magneticstructure, preferably laminated, supported immediately adjacent andparallel to the bars or tubes and with the open ends of the ma 1 neticstructure slots facing the ladle bottom. The coils and the magneticstructure are so arranged that the inductive effect is concentrated overthe length of the interior surface of the bottom wall, the stirringdevice extending in either direction beyond the bottom Wall, however.

For an understanding of the invention principles, reference is made tothe following description to a typical embodiment thereof as illustratedin the accompanying drawing. In the drawing:

Fig. l is a vertical sectional view through a molten metal holding,refractory lined ladle embodying the invention;

Fig. 2 is a partial transverse sectional view of the bottom wall, takenon the line 22 of Fig. 1; and

Figs. 3 and 4 are views similar to Fig. 2 illustrating alternativeconstructions of the sloping bottom wall.

In the drawings, the invention is illustrated, by way of specificexample only, as applied to the inductive stirring of molten steel in arefractory lined ladle, it being understood that the invention is not inany way limited to this particular application but may be used whereverit is desired to stir electrically conductive fluid material in anycontainer. Referring to Fig. l, a ladle is shown as comprising arefractory lining 11 supported in an outer metal shell or casinggenerally indicated at 12. i

An angular cross section framework 13 at the upper end of ladle 1i andsecured to shell 12, is provided to receive a suitable cover (not shown)for the ladle. The lining 11 is formed with a suitable pouring lip 14adjacent which shell 12 is suitably cut away. If desired, pour lip orspout 14 may be provided with a water-cooled lintel, such as shown anddescribed in the copending application of I. Harter et al., Serial No.316,446, filed October 23, 1952, for the purpose of promotingdevelopment of a slag dam by chilling floating slag during pouring. Thebath within ladle 10 may have its upper surface locally heated by arcsplayed thereon from arcing electrodes 50 which, in practice, may extendthrough the cover for the ladle into proximity with the upper surface ofthe bath.

Intermediate the height of casing 12, a shelf or support bracket 16 issecured peripherally thereto to removably support ladle ill on asupporting flange 17 of a suitable cradle or the like 15. Cradle may bea stationary holding station for ladle 10 or may be a tiltably mountedstructure for tipping the ladle 10, about an axis passing transverselythrough lip 14, to pour molten metal from the ladle.

Ladle 10 is in the form of a truncated cone of substantial axial length.The frusto-conical lining 11 includes a relatively deep rear wallsegment 18 diametrically opposite pouring lip 14, whereas the front wallsegment 19 is substantially shorter than segment 18. The lower end ofthe ladle is closed by a bottom 21. In diametric cross section, ladleIt) may be either circular or elliptical.

. eral member 24.

tic:

The inductor device, generally indicated at 30 and described more fullyhereinafter, is mounted in cradle 15, to extend in parallel spacedrelation to the bottom wall 20 of a ladle it) supported on cradle flange17. The side wall portion of metal casing 12 is preferably divided intoan upper section 2.2 and a lower section 23, the latter comprisingsubstantially all that part of the casing sidewalls disposed within thehigh strength field of inductor 34). While upper casing portoin 22 maybe any suitable metal or alloy, lower section 23, at least, if of anon-magnetic metal material, such as some of the stain less steels.

The casing support for bottom 2!? is necessarily interposed directlybetween inductor 39 and the molten metal ladle it). Thus, beingcompletely in the inductor field and immediately adjacent the inductorthis part of the casing has the most effect in absorbing or dissipatingthe l'nld flux.

in accordance with the invention, the field losses in the support forbottom 20 are minimized, if not substantially eliminated, by formingthis support as a series of spaced, subst it' ly parallel slats or bars25. These bars, which preferably re non-magnetic metal, are supported ateach end in electrically insulated relation on a periph- Slats 25 may besolid or tubular, and of any desired cross sectional shape.

in the arrangement of Fig. 2, the slat structure may comprise aplurality of substantially parallel solid bars 25 extending forwardlyand upwardly in supporting engagement with the outer surface of bottomit} and spaced to provide slots 26 therebetween. lternatively, the slatstructure may comprise a plurality of spaced substantially parallelrectangular tubes 27 extending forwardly and upwardly in supportingengagement with bottom 2% and likewise forming slots 26 thcrebetween.This arrangement is shown in Fig. 3. A further slat arrangement is shownin Fig. 4 as comprising a plurality of cylindrical tubes 28, likewisearranged in substantially parallel spaced relation and extendingforwardly and upwardly in supporting engagement with ladle bottom 20,the spaced tubes 23 forming slots 26 therebetween.

The slat structure supporting the refractory bottom 29 provides for flowof cooling air upwardly and forwardly along the under surface of bottom2? and through the slots 26. Due to the upwardly extending relation ofthe bottom and the slats, there is a natural circulation of cooling airover the outer surface of bottom 2:) which tends to reduce the ambienttemperature adjacent the ladle bottom wall. The bars 25, or tubes 2'7 or28, may

, be bolted to flange 24 with the interposition of suitable insulatingsleeves and washers. To enhance the cooling effect, air from a suitablesource (not shown) may be blown through slats 27 or 28 or through theslots 26 between the slats 25, 27 or 28.

By dividing the support for the bottom 2% into spaced individualelements, the magnetic circuits are interrupted and the field absorptionthus greatly reduced. Also, by insulating the slats from each other andfrom casing section 23, the paths for current flow are likewiseincomplete. Hence, the field losses in the bottom wall support are atleast minimized and may be substantially eliminated. Thus, the net powerinput required to produce a given stirring effect is greatly reduced.

The inductive stirring arrangement 31) is supported in the cradle 15,coming into operative relation with ladle ltl only when the latter issupported in cradle 15. Thus, the number of inductive stirring devicesrequired is reduced, as only one is required at each holding station andat each pouring station. Also, the weight of the ladle structure isreduced by virtue of the fact that the inductive stirring arrangementdoes not form part of the ladle structure, and ladle lb can be movedwithout the necessity of disconnecting high amperage electrical leads.

Referring again to Fig. l, inductor 30 comprises a preferably laminatedfield structure secured at one end to the lower wall or platform 31 ofcradle and extends upwardly and forwardly parallel to ladle bottom 20.The upper end of structure 3% is secured to the forward wall 32 ofcradle 15. inductor St is so arranged in cradle 15 that, when ladle it)is supported in the cradle, there is a slight space or gap betweenadjacent parts of inductor 3i] and the slat structure 25 supporting thebottom of the ladle. Adjacent its lower end, inductor structure Si isprovided with a plurality of winding slots 33 usually normal to bottom2b and opening upwardly. T he intermediate portion of the fieldstructure is provided with a plurality of deeper slots 34, likewiseusually normal to and opening toward bottom 2%, and which havesubstantially twice the depth of slots 33. The upper end of structure 36is provided with a plurality of shallower slots 36, substantially equalin depth to slots 33, and usually normal to and opening toward bottom2%. it will be noted that the faces of slots 33 adjacent bottom 2d arein the same plane as the corresponding faces of the deep slots 34whereas the bottoms of slots 36 are in the same plane as the bottoms ofslots 34.

A first series of coils or coil sections 35 are placed in the inner endsof slots 34 and 3d, and a second series of coils or coil sections 41;are placed in the slots 33 and in the outer ends of slots as overlyingthe coils or coil sections 35. By reference to Fig. 1 it will beobserved that, adjacent the lower rearmost portion of bottom 2t], is afirst series of inductive windings relatively close to the slottedsupporting structure. Beginning at a point in a plane which, ifprojected parallel to the side wall of slots 34 would substantiallyintersect the lower rear corner edge between wall segment 13 and bottom2%, the concentration of the inductive windings is double in the slots34, this concentrated winding extending to near the upper edge of bottom2b where the latter merges with forward ladle wall segment 15 From thispoint onward, a single series of inductive windings is disposed in theslots 36 and is relatively more widely spaced from the slotted ladlebottom.

With the described inductive stirring arrangment, an inductive effect onthe molten metal is provided which is at its greatest strength andconcentration along the major portion of the upward length of bottom 20,beginning at the lower edge of this wall. In advance of this lower edge,a reduced inductive effect is provided which is, nevertheless,concentrated by being provided by coils closely adjacent the bottomwall. At the upper forward edge of bottoi 1 2b, the inductive effect isprovided in substantially reduced amount by virtue of the single seriesof inductive windings in slots 36 which are spaced substantially frombottom Thereby, a variable inductive effeet is provided which acts onthe molten metal as the latter approaches the junction between segment18 and bottom 29 durin its circulation, this inductive effect beingsubstantially increased as the metal begins to move upwardly along thebottom 2 Subsequently, the inductive effect is substantially reducedadjacent the upper end of bottom 20 so that less moving force isimparted to the circulating molten metal as it begins to move upwardlyalong the relatively short forward wall segment 19. This provides asubstantially uniformly effective force on the molten metal, the coilsin slots 33, by virtue of being immediately adjacent the bottom wall,exerting a greater effect on the metal than the coils in slots 36. Themaximum moving effect on the molten metal is concentrated along themajor portion of sloping bottom 26 by virtue of the double layers ofcoils laid in deep slots 34.

This arrangement is of particular importance in pro viding a sufficientmotion for the molten metal in such a uniform manner as to eliminate orreduce the possibility of erosion of lining 12 due to the motion of themetal. Also, the moving efiect along wall segment 19, by being reducedcompared to that along wall 26 and along wall 18, will also result insuiiicient motion to sweep the slag back from lip 14.

The coils 35 and 40 are suitably energized with either low frequencypolyphase A. C. or progressively switched D. C. to produce an inducedfield substantially constant in strength moving upwardly along bottom2%). In the case of energization with low frequency, polyphase A. C.,the coils are so wired that, at any given instant, the coils 4t lying inshallow slots 33 would produce a pole of a given polarity (south, forexample), the coils 35 and 4t lying in deep slots 3 3 would produce anorth pole, and the coils 35 lying in shallow slots 35 would produce asouth pole. With polyphase energization, there will thus be produced aninduced polarity moving from left to right along bottom 2%.Approximately the same elfect is obtained by using D. C. energizationwith progressive mechanical switching.

During the described stirring motion of the molten metal, the lattersweeps upwardly along wall segment 19 and then rearwardly away fromspout 14 and into the region of the are or arcs from electrode 50. Thus,the metal is continually circulated past the hot spot on the surface ofthe bath before returning to the bottom of the bath. This promotesuniformity of temperature throughout the bath and prevents there beingany temperature gradient between the surface and the bottom of the bath.The rearward motion effected along the bath surface tends to keep theslag held back from lip 14. During pouring of ladle 1d, the intensity orspeed of the field provided by inductor 3t may be temporarily increased,by raising the frequency if A. C. is used or speeding up the switchingif D. C. is used, to insure the slag being held back from the pouringlip 14- by the stirring motion.

The sloping bottom 20 in association with wall segment 19 provides aneasy transition Zone for the moving molten metal in passing from thebottom upwardly along wall segment 19. While arc electrodes Sll havebeen shown as the local heating means, it should be understood that theheating means may be other than the arcing electrodes, as for example agas flame.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventionprinciples, it will be understod that the invention may be embodiedotherwise without departing from such principles.

We claim:

1. A container for electrically conductive fluid material, havingupwardly extending opposite wall portions and a bottom wall slopingupwardly from the lower periphery of one of said wall portions to thelower periphery of the other wall portion; and electric field producingmeans arranged adjacent the under surface of said bottom wall to induceelectromotive forces in the fluid material to stir the latter.

2. A container for electrically conductive fluid material, havingupwardly eritending opposite wall portions and a bottom wall slopingupwardly from the lower periphery of one of said wall portions to thelower periphery of the other wall portion; and electric field producingmeans arranged adjacent the under surface of said bottom wall to induceelectromotive forces in the fluid material to move the latter upwardlyalong said bottom wall.

3. In combination, a container for electrically conductive fluidmaterial, having upwardly extending opposite wall portions and a bottomwall sloping upwardly from the lower periphery of one of said wallportions to the lower periphery of the other wall portion; a cradleremovably supporting said container; coil means mounted in said cradleand arranged along the under surface of said bottom wall of a containersupported in the cradle; and means for electrically energizing said coilmeans to induce electromotive forces in the fluid material to effectmotion of the latter.

. 4. In combination, a container for electrically conductive fluidmaterial, having upwardly extending opposite wall portions and a bottomwall sloping upwardly from the lower periphery of one of said wallportions to the lower periphery of the other wall portion; a cradleremovably supporting said container; coil means fixedly mounted in saidcradle and arranged along the under surface of said bottom wall of aconta ner supported in said cradle; and means for electricallyenergizing said coil means to induce electrornotive forces in the fluidmaterial to effect motion of the latter upwardly adjacent said bottomwall.

5. A container for electrically conductive fluid mate rial, havingupwardly extending opposite wall portions and a bottom wall slopingupwardly from the lower periphery of one of said wall portions to thelower periphery of the other wall portion and having slots in its undersurface; and electric field producing means arranged adjacent said slotsto induce electromotive forces in the fluid material to stir the latter.

6. In combination, a container for electrically conductive fluidmaterial, having upwardly extending opposite wall portions and a bottomwall sloping upwardly from the lower periphery of one of said wallportions to the ,lower periphery of the other wall portion and havingslots in its under surface; a cradle removably supporting saidcontainer; coil means fixedly mounted in said cradle arranged along theunder surface of said bottom wall of a container supported in saidcradle; and means for electrically energizing said coil means to induceelectromotive forces in the fluid material to eflect motion of thelatter.

7. In combination, a pouring container for electrically conductive fluidmaterial, having upwardly extending opposite wall portions, a bottomwall sloping upwardly from the lower periphery of one of said wallportions to the lower periphery of the other wall portion and a pouringlip; a cradle removably supporting said container; electric fieldproducing means arranged adjacent the under surface of said bottom wallof a container supported in said cradle to induce electrornotive forcesin the fluid material to stir the latter, and supported for unitarymovement with the container; and means mounting said cradle for tiltingabout an axis passing through the container pouring lip.

8. in combination, a pouring container for electrically conductive fluidmaterial having upwardly extending opposite wall portions, a bottom wallsloping upwardly from the lower periphery of one of said wall portionsto the lower periphery of the other wall portion and having slots in itsunder surface, and a pouring lip; a cradle removably supporting saidcontainer; electric field producing means arranged adjacent said slotsto induce electromotive forces in the fluid material to stir the latter,

8 and supported for unitary movement with the container; and meansmounting said cradle for tilting about an axis passing through thecontainer pouring lip.

9. A tiltable pouring container for electrically conduca tive fluidmaterial having upwardly extending opposite wall portions formed with apouring lip, and a bottom wall of non-magnetic material sloping upwardlyfrom the lower periphery of one of said wall portions to the lowerperiphery of the other wall portion; and electric field roducing meansarranged adjacent the under surface of said bottom wall to induceelectromotive forces in the fluid material to move the latter upwardlyalong said bottom wall, and supported for tilting movement with thecontainer.

10. A tiltable pouring container for electrically conductive fluidmaterial having upwardly extending side walls formed with a pouring lip,and a sloping bottom wall, including non-magnetic, electrically isolatedelements forming slots in the under surface of the bottom wall; andelectric field producing means arranged adjacent said slots in the undersurface of said bottom wall to induce electromotive forces in the fluidmaterial to move the latter along said bottom wall, and independentlysupported for unitary tilt ng movement with the container.

11. in combination, a pouring container for electrically conductivefluid material having upwardly extending side walls formed with apouring lip, and a sloping bottom wall, including non-magnetic,electrically isolated elements forming slots in the under surface of thebottom "'wall; a cradle removabb supporting said container; coil meansarranged adjacent said slots along the under surface of said bottom walland fixedly supported in said cradle, for inducing electromotive forcesin the fluid ,material; and means mounting said cradle for tiltingmovement about an axis passing through the container pouring lip.

References tilted in the file of this patent UNITED STATES PATENTS

1. A CONTAINER FOR ELECTRICALLY CONDUCTIVE FLUID MATERIAL, HAVINGUPWARDLY EXTENDING OPPOSITE WALL PORTIONS AND A BOTTOM WAL SLOPINGUPWARDLY FRM THE LOWER PERIPHERY OF ONE OF SAID WALL PORTIONS TO THELOWER PERIPHERY OF THE OTHER WALL PORTION; AND ELECTRIC FIELD PRODUCINGMEANS ARRANGED ADJACENT THE UNDER SURFACE OF SAID BOTTOM